Blood test developed to detect risk of genetic disorder in foetus

Monday 18 September 2006 19.06 EDT
First published on Monday 18 September 2006 19.06 EDT

Doctors have developed a non-invasive test that can help determine if a foetus is at risk of genetic disorders six weeks into the pregnancy.

The blood test - which determines the foetus's sex - halves the need for further invasive tests, which result in miscarriages in up to one in 50 pregnancies, and ensures the conditions can be detected up to nine weeks earlier than at present.

The new technique, non-invasive prenatal diagnosis, is being used to help determine if foetuses are affected by conditions which usually only affect boys such as the blood clotting disease haemophilia.

But researchers are also developing the technique to diagnose cystic fibrosis and Down's syndrome within three to five years. The test involves work on tiny amounts of "free foetal DNA" which make up 5% of a mother's DNA in her blood during early pregnancy.

Researchers analyse this to identify genes that are present in the father and can be passed on to the foetus.

Lyn Chitty, a reader in genetics and foetal medicine at the Institute of Child Health and University College London, who headed the research, said: "The advantages of this test are clear when used in women at high risk of a genetic disorder. "It allows for earlier determination of foetal sex than was previously possible using either chorionic villus sampling or ultrasound. It avoids the risks associated with invasive testing in about half of the women." Dr Chitty, who will present her research at the annual meeting of the British Society of Human Genetics in York today, said that she anticipated a non-invasive test for cystic fibrosis could be developed within five years.